What this test measures
The Absolute Eosinophil Count (AEC) is the actual number of eosinophils per microlitre of blood — calculated from total leucocyte count × eosinophil percentage. Adult normal range is 40–500 per µL. Eosinophils are white blood cells specialised in defending against parasites and modulating allergic responses.
Unlike the eosinophil percentage (which is a relative number and can be misleading if the total WBC is abnormal), the absolute count is the clinically meaningful figure. Modern automated analysers measure this directly. The result is reported with the standard CBC differential or as a standalone AEC.
Why it matters
In India, raised AEC is common and the differential diagnosis is broad: allergic rhinitis and asthma (the most common cause in urban areas), parasitic infestation (filaria, hookworm, ascaris, strongyloides — still endemic in many regions), drug reactions (especially to antibiotics, anticonvulsants), atopic dermatitis, and rarer disorders (hypereosinophilic syndrome, eosinophilic gastroenteritis, lymphoma, eosinophilic granulomatosis with polyangiitis).
Very high AEC (>1,500) sustained over weeks warrants further workup — peripheral smear for parasites, stool examination, IgE level, chest X-ray, and sometimes a haematology consultation. In children with chronic cough or skin rash, AEC is one of the first tests ordered to support an allergic or parasitic cause.
How to prepare
No fasting required. Avoid steroids (oral or injected) for at least 1 week before testing — corticosteroids dramatically lower eosinophils within hours and can mask elevated counts. Disclose recent antiparasitic treatment, allergies, and asthma medications.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Absolute Eosinophil Count (cells/µL (or ×10⁹/L))[1][2] | 40–500 cells/µL | Low or zero eosinophil count is common with steroid use, acute bacterial infection, severe sepsis, and Cushing syndrome. Generally not clinically significant. | Mild rise (500–1,500): allergic rhinitis, asthma, eczema, drug reactions, mild parasitic infestation. Moderate (1,500–5,000): significant parasitic infection (filaria, strongyloides, ascaris), drug reaction, eosinophilic asthma. Marked (>5,000): hypereosinophilic syndrome, eosinophilic leukaemia, eosinophilic granulomatosis with polyangiitis (Churg-Strauss), lymphoma, advanced parasitic disease. Persistent eosinophilia >1,500 lasting >6 months needs specialist evaluation. |
AEC interpretation and common causes
| AEC (cells/µL) | Severity | Common causes |
|---|---|---|
| < 40 | Eosinopenia | Steroid use, acute infection, Cushing — usually not significant |
| 40 – 500 | Normal | — |
| 500 – 1,500 | Mild eosinophilia | Allergic rhinitis, asthma, atopic dermatitis, drug reaction |
| 1,500 – 5,000 | Moderate eosinophilia | Parasitic infection, drug reaction, eosinophilic asthma |
| > 5,000 | Marked eosinophilia | Hypereosinophilic syndrome, leukaemia, lymphoma, severe parasitic disease, EGPA |
Frequently asked questions
Why is my AEC raised?
In Indian adults, the commonest causes are allergic rhinitis, asthma, atopic dermatitis, and parasitic infestations (filaria, hookworm, strongyloides). Drug reactions and skin disorders are also common.
Do I need to fast?
No.
My AEC is 800 — is that a problem?
800 is mildly elevated. The most common explanation is allergy (rhinitis, asthma, eczema). If you have symptoms, allergen testing and a treatment plan should follow. If completely asymptomatic, a single mildly raised value can be observed and rechecked.
What is hypereosinophilic syndrome?
A rare condition where eosinophil count is persistently >1,500/µL for more than 6 months without an identifiable cause, with evidence of organ damage. It needs specialist haematology care.
Why do steroids lower the eosinophil count?
Corticosteroids cause eosinophils to redistribute out of the circulation and increase their destruction. The drop can be dramatic within hours and can mask real eosinophilia. Always check AEC before starting steroids.
Can intestinal worms cause raised AEC?
Yes — and worm infestations are still common in many parts of India. Hookworm, ascaris, strongyloides, and filaria all raise AEC. A stool examination is usually the next step.
How is the test done?
A standard EDTA blood tube is processed on an automated haematology analyser. Results are reported as both absolute count and percentage.
How long does the report take?
AEC is reported within 2–4 hours along with the CBC.
Related Hematology / Anemia tests
Tests commonly ordered alongside Absolute Eosinophile Count, or that help interpret an unexpected result.
Sources & references
- NCBI StatPearls — Eosinophilia · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Eosinophil Count · accessed 2026-05-30T00:00:00.000Z
- American Society of Hematology — Eosinophilic Disorders · accessed 2026-05-30T00:00:00.000Z
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